Phosphor bearing surface



u 23, 1960 J. B. HINSON' 2,950,222

PHOSPHOR BEARING SURFACE Filed may 20. 1958 THIN ACRYLIC INVENTOR. JAY B. H/NSON A TTOENEY i niteci This invention relates to phosphor bearing and fluorescent bearing surfaces which carry the phosphors or fluorescent materials so as to yield visible light in a darkened space after being exposed to light, or activated by ultraviolet light.

Such surfaces have many uses, such as to light ships engine rooms when power fails, to light stirs and doorways in houses when other light fails, to provide guide lights to indicate in the dark Where electric light switches stand, and many minor uses. Farms and industrial plants will find many uses as directional indicators and safety markers.

Such surfaces have attempted to be used in the past but have uniformly proved unsatisfactory, failing to meet even the minimum specifications set up by the armed forces, Navy-Army-Air Force, which attempt to prescribe a test defining the minimum of practical utility.

Even the imperfect materials hitherto put out had to be produced with great care under factory supervision.

According to the present invention the desired surfaces may be prepared at home with commercially available materials, or with materials adapted to be shipped and sold over the counter, in the form of the liquids in cans, and other materials readily available and obtainable.

The pigmented solution may preferably be packaged in a plastic bag, such as double polyethylene bags made double with separately tied necks to carry liquids for analogous purposes. These bags have been found to be more practical and more convenient than cans in View of the characteristics of pigments generally, and of insoluble pigments, in particular. The luminouspigment s preferably carried in the form of a light-bodied paste m a liquid carrying preferably a permanently flexible grade of acrylic ester resin.

While the viscosity of the permanently flexible grade of resin solution will prevent the separation of the insoluble pigments there will be a settling of the heavier A particles in the course of the shelf life of such a pigmented solution.

The economy and convenience of packaging luminous paints in this form is apparent from the ease of thoroughly mixing the ingredients back to the original consistency with minimum loss by evaporation of the volatile thinners. The hand mixing of the 6 to 12 ounce pigmented solution in a bag can be done in a matter of a few minutes by kneading the partly full bag and this time may be shortened by placing the plastic bag (with its contents) in hot water, preferably above 160 F. If this is done the outer bag should be thoroughly dried before opening to pour out the contents.

In the form illustrated in some detail, a standard type of 200 mesh to 325 mesh (and fines) of approximate proportions of calcium sulfide 75 percent and strontium sulfide 25 percent mixture is the light-giving element, such as is set forth in Stern Patent No. 2,475,437 of July 5, 1949, and this is carried on bright aluminum foil backing.

The aluminum foil used may advantageously be the ordinary household aluminum foil, approximately 0.0005 inch thick and otherwise suitable for the purpose in hand. Foil of that thinness is found to be flexible enough to be fitted closely to the irregularities and roughnesses of any surface considered suitable to take a priming coat of ordinary painting.

tates atent O Patented Aug. 23, 1960 ice This thin foil is applied to the surface from which light is desired and preferably is held thereby a suitable adhesive or masking tissue provided with adhesive on both sides. The foil, if need be, is forced into the irregularities of the perfectly dry surface, as by a brush like a stippling or stencil brush which forces it into the cracks and surface irregularities, spans large openings like knot holes, and, in other ways, provides a continuous watertight aluminum surface to receive and hold the paint.

This surface need not be horizontal when applying the luminous paint, for the paint described below in detail will adhere to a vertical surface. Another convenient method of applying the foil to the prepared adhesive coated surface is to press it with a portion of turkish towel balled up in ones hand and rub over the foil, forcing the foil into a secure and set position on the base surface.

On this clean aluminum surface is spread, usually by brush strokes, a foundation coat of suitable lacquer applied at room temperature, preferably 70 to F., preferably thin, usually a permanently flexible acrylic base to Withstand the weather although vinyl resin base is nearly as satisfactory for inside work. This coat when dry is almost tacky and flexible so that the coated aluminum when cut leaves a turned-in edge of the resin, and seals the edges at room temperatures against penetration of moisture and is a barrier against creeping, as by capillary action, of dampness, mold, and mildew.

On this foundation When dry, although having a slight permanent tack, is spread a thicker coat of lacquer carrying the phosphor or fluorescent powder. The same permanently flexible lacquer may be used to carry the pigment as was used in the foundation coat. When applying pigmented solution, the optimum temperature range should be 70 to 100 F.

The phosphor or fluorescent material bearing coat is diflicult to spread evenly unless a procedure described below is followed. That procedure, briefly, involves spreading the phosphor bearing coat by a relatively stiff brush having bristles standing parallel to the axis of the handle, so that most of the bristle ends rest vertically on the surface to be coated and the brush spreads a limited load of the liquid phosphor bearing material by the axial ends of the bristles, by a continuous circular movement with the pigment-ladened brush until no sag or flow-out occurred in the applied pigmented solution.

It is found that the liquid carrier deposits the phosphor particles very evenly in one coat when the brush is swung and swirled in overlapping circles against the surface and no more than touches any dry previously applied coating. The liquid phosphor bearing solution deposited on the ends of the bristles to a depth of approximately inch is preferably and easily distributed to a thickness of 0.006 to 0.008 inch solids when dried on the metal surface.

Over the dried pigment-bearing acrylic resin is spread a protecting coat, preferably Weatherproof and hard enough so as not to be tacky. A general purpose tough acrylic resin seems the best material, but vinyl resin has proved useful, and other resins may be used.

A skillful Workman can apply the finishing or protecting coat with a brush, preferably a camels hair brush, but a sprayed-on coat is usually simpler and more satisfactory and easier to apply evenly. Usually two or more sprayedon coats of aerosol spray are needed for adequate thickness.

Th foundation coat keeps the foil from oxidizing and holds the pigment in the pigment-coat clear of the aluminum, thus avoiding chemical reaction, and, moreover, permits any light emitted from the back of the phosphor particles to be reflected forward, adding to the total light-giving value of the activated luminous pigment.

It is found that this series of coatings renders the finer' particles of phosphors as efficient as the coarser particles hitherto deemed to be the most eflicient in yielding light. The light lumens of the present invention are brighter .than required in government specifications which have hitherto been regarded as unattainable- -Moreover, the light-giving power is longer lasting by several times than hitherto deemed possible. Accelerated weathering tests have shown usable light was sustained, under darkened conditions, and without reactivation for periods as long as 96 continuous hours whereas prior material of same type has been limited to maximum of 10 to 12 hours of yielding measurable light.

Other materials may replace the aluminum foil, such as aluminum paint and white lacquer paint, but lack most of its advantages, although some organic films are even more flexible and carry other advantages. The safest resin solvents for an inexperienced worker I to use as lacquer ingredients are described in some detail below, so that such workers will not face unexpected dif- 'ficulties in using the lacquers, but experienced workers skilled in the art may prefer other. organic solvents or other proportions to meet special conditions, choosing from the upwards of fifty organic solvents listed by some I chemical manufacturers.

A suitable foundation coat is commercially available, of the following composition by volume:

quested for additional solvent or thinner. These chemicals are commercially available and are preferably used in the percentage ratio as shown in formula. This composition is not recommended for spraying. a ,7 This foundation coating is appliedbest by brushing on with a brush full of. solution in one coat, allowing ten minutes or more for evaporation from the applied coating .of the volatile vapors The resin solids preferably are such as remain tacky to touc at room temperatures. This applied foundation coat is usually satisfactory when 0.001 inch thick. Objects, forms and shapes, may be dippedrwith the same good results obtained by brushing. 1 a a The phosphor or pigment bearing coat is usually satisfactory When 0.006 to 0.008 inch'thick. .This thickness is readily obtained in a one coat application, as described in some detail below. A. a

The same resin solution may be superposedon the foundation coat to obtain the optimum pigmented mixture, with proportions as follows (proportions are not critical and may be adjusted to meet specific needs):

' Foundation coat solution (percent by volume) ..65 (clear) Dry pigment (percent by volume) 35.

Two medium spray coats of the following formulation, '65

by volume, usually gives the approximate 0.001 inch thickness.

Acrylic ester resin (B-72) 24% solids. H Toluol (solvent) 56%. MIBK (thinner) 10%.

Xylol (thinner) 10%.

This spray solution may be brushed on (by strokes) over the phosphor bearing coatafter the phosphor coat is thoroughly dry.

'It has been supposed that phosphors deteriorated on storage even in dark bottles, so that they were discarded after six months.

According to the present invention it is found that the 5 completely sealed in particles have a useful life of years.

Moreover, the aluminumbacking foil, or other reflecting backing, reflects activating light into the backs of the particles so that their light giving activated life is multiplied by a factor of ten over anything hitherto obtained,

and the finer particles hitherto regarded as less" efficient are found to be the most eificient.

Five minutes daylight activation gives adequate activation for as long as 96 hours of light emitting. a Apparently light alters the electrical charge on'the phosphor which is insulated by 0.001 inch of insulator from the aluminum. I The aluminum thereby acquires an op- -posite charge like on electrical condensers. That charge is immediately conveyed away by the highly conductive -aluminum, thereby stabilizing the new charge on the phosphor to give prolonged light. a e

Other features and advmtages will hereinafter appear. In the accompanying drawings: 1 Fig. 1, a diagrammatically exploded section, shows a wall, greatly enlarged, carrying the superimposed coatings.

Fig. 2 shows the superposed layers, successively broken away to show the underlying. layers. 7

The present invention is shown as embodied in a wall, in which the wall 10 carries a sheet of aluminum foil 11, which may be household? foil 0.0005 inch thick,

and which is held to the .wall by a layer of suitable adhesive 12. The double faced adhesive strip of Bennett Patent No. 2,191,704 has been found very satisfactory. In that patent is shown a strip of adhesive carried releasably on a carrier strip and unrolled as applied to the :face. The carrier strip serves to protect the adhesive strip on the foil until used when it is stripped 03 to perrnit the adhesive to be pressed on the wall 10.

1 Upon the foil 11 is spread a thin continuous foundation flexible coating of an acrylic. resin 13. A suitable coating material was that described above. An acrylic ester resin of similar properties of DuPont Company was equally satisfactory. Aluminum-coated copper foil 'was usuable under many conditions instead of the aluminurn foil.

The foundation coat 13 carries the pigment or phosphor bearing coat 14, and this in turn carries the finishing coat 15. The phosphor bearing or pigment coat is "usually satisfactory when it is 35% pigment and 65% carrier liquid. I

The resin and phosphor coatings of the present Invention are well adapted to be applied to'an asbestos sheet to serve as a warning of undesired rise of tempera 'ture on the opposite side of the sheet of asbestos. The phosphor becomes self luminous. when the temperature 'rises to a known point, so when the surface of the asbestos reaches that point by transmitted heat, the phosphor glows as a warning. The front surface tempera- 'ture of the asbestos reaches that glow point at'a temi perature below that of the heated back'depending on the thickness of the asbestos. The difference in temperature may be varied by varymg the thickness or the compactness of the asbestos body which GS graded by past experience.

The phosphor pigment used was the. commercial grade of which 99% passed a ZOO-mesh sieve, and 40% passed (a 325-mesh sieve, and were fines.

1 Having thus described certain embodiments of the mvention in some detail,what is claimed is: y 1. The process of making a light-yielding surface which'consists in coating a base sheet aluminum faced material with a clear resin consisting of soft acryhc resin in solution for a foundation coat, coating the founidation coat with a suspension of a light yielding p ginent material to a greater thickness by applying the pigmeat-bearing lacquer by a brush having bristles bearing vertically on the foundation coat, and applying a finishing transparent coat by appiying a finishing lacquer by a spray of lacquer material.

2. The process of making a light-yielding surface which consists in coating a base sheet of clean aluminum foil thinner than 0.001 inch with a clear soft acrylic resin in solution for a foundation coat, coating the dry foundation coat with a suspension of a light-yielding pigment material to a greater thickness by applying the sealing pigment-bearing lacquer by a brush having bristles bearing vertically on the foundation coat, and applying a finishing transparent coat by applying a finishing lacquer by a spray of lacquer material.

3. The process of making a light-yielding surface which consists in applying an exposed face of a masking sheet carrying a universally adhering adhesive to a supporting structure, removing the cover sheet of the masking sheet to expose the second adhesive carrying side to expose the second adhesive face, and applying to said second adhesive face a sheet of aluminum foil carrying a foundation coat of soft acrylic resin, an acrylic resinbound light-giving pigment layer, and a transparent finishing coat.

4. The combination with a flexible aluminum faced backing sheet, of a first transparent soft acrlic resin coating thereon, a resin-bound phosphor-bearing coating, consisting principally of phosphor fines, on said first transparent coating, and held clear of the backing by said first coating, and a protective transparent resin coating lying on the phosphorbearing coating and serving to protect it.

5. The combination with a flexible aluminum foil backing sheet, of a first permanently soft transparent resin coating thereon, an acrylic resin-bound phosphor-bearing permanently soft coating on said first transparent coating and the phosphor consisting principally of fines and held clear of the backing by said first coating, and a protective transparent weather-resistant resin coating lying on the phosphor-bearing coating and serving to protect it.

6. The combination with a flexible aluminum backing sheet, of a first transparent resin coating thereon, an acrylic resin-bound phosphor-bearing soft coating on said first transparent coating, said phosphor consist-ing principally of fines, and held clear of the backing by said first coating, and a protective transparent resin coating lying on the phosphor-bearing coating, serving to protect it, and an adhesive layer on the back of the backing sheet.

7. The combination with a flexible aluminum foil backing sheet, of a first permanently soft transparent acrylic resin coating thereon, a resinbound phosphorbearing permanently soft acrylic-bound coating on said first transparent coating, said phosphor consisting principally of fines, and held clear of the backing by said first coating, and a protective transparent weather-resistant resin coating lying on the phosphor-bearing coating and serving to protect it, and an adhesive layer on the back of the backing sheet.

8. The combination with a layer of phosphor particles, principally fines, imbedded in an insulating transparent soft resin, of a backing having an aluminum face supporting the phosphor layer, a continuous thin layer of flexible acrylic resin spacing the phosphor resin from the aluminum, and a flexible transparent resin covering the phosphor layer to protect it.

References Cited in the file of this patent UNITED STATES PATENTS 1,532,783 Sheppard et a1. Apr. 7, 1925 2,387,512 Hilberg Oct. 23, 1945 2,740,050 Schultz Mar. 27, 1956 2,822,288 Harvey et a1. Feb. 4, 1958 

3. THE PROCESS OF MAKING A LIGHT-YIELDING SURFACE WHICH CONSISTS IN APPLYING AN EXPOSED FACE OF A MASKING SHEET CARRYING A UNIVERSALLY ADHERING TO A SUPPORTING STRUCTURE, REMOVING THE COVER SHEET OF THE MASKING SHEET TO EXPOSE THE SECOND ADHESIVE CARRYING SIDE TO EXPOSE THE SECOND ADHESIVE FACE, AND APPLYING TO SAID SECOND ADHESIVE FACE A SHEET OF ALUMINUM FOIL CARRYING A FOUNDATION COAT OF SOFT ACRYLIC RESIN, AN ACRYLIC RESINBOUND LIGHT-GIVING PIGMENT LAYER, AND A TRANSPARENT FINISHING COAT. 